Mining machine with apparatus for conveying pressurized fluid between movable frames

ABSTRACT

A sliding fluid joint for transfer of hydraulic fluid described in relation to a mining machine. The mining machine has a main frame with drive means for propelling the machine. A second frame, or sump frame, extends forwardly from the main frame. A rotary drum for cutting and breaking material out of a mine face is pivotally mounted on the front end of the sump frame. The sump frame is slidably mounted on the main frame so the propelling means may be locked and the rotary drum advanced into the mine face by moving the sump frame forward away from the main frame. The main frame carries an electric motor driving a hydraulic pump for supply of fluid under pressure to fluid activated devices such as cylinders and hydraulic motors which are mounted on the main frame and on the sump frame. To connect the hydraulic pump on the main frame to fluid activated devices on the movable sump frame, sliding fluid joints are provided which eliminate the need for long flexible hose. The joints permit the frames to move relative to each other while maintaining a constant flow of fluid between the devices on the main frame and those on the sump frame. The sliding fluid joint comprises a cylinder and a longer hollow rod which passes longitudinally through the cylinder. Fluid flows into the rod and passes through holes in the rod into the cavity formed between the rod and the cylinder. From there the fluid flows out of an opening in the cylinder sidewall to the fluid activated devices on the second frame. This structure allows the rod and cylinder to move relative to each other without affecting the flow of fluids between the main frame and sump frame.

United States Patent 1 1 Cilles i 1 MINING MACHINE WITH APPARATUS FOR CONVEYING PRESSURIZED FLUID BETWEEN MOVABLE FRAMES [52] US. Cl. 299/75; 285/62; 285/302; 299/64 [5 1] Int. Cl. E210 27/24 [58] Field of Search 285/137 R. I63, I65, 302; 60/l77. I84; 299/59-62. 7l-76; l73/27 [56] References Cited UNITED STATES PATENTS 732.326 6/1903 Unanue 299/62 X 3.209.786 l0/l965 Daniels 285/302 X Primary E.\'aminerErnest R. Purser Attorney. Agent. or Firm-Steven R. Gustafson; John M. Lorenzen [57} ABSTRACT A sliding fluid joint for transfer of hydraulic fluid described in relation to a mining machine. The mining machine has a main frame with drive means for propelling the machine. A second frame. or sump frame.

[451 Apr. 8, 1975 extends forwardly from the main frame. A rotary drum for cutting and breaking material out of a mine face is pivotally mounted on the front end of the sump frame. The sump frame is slidably mounted on the main frame so the propelling means may be locked and the rotary drum advanced into the mine face by moving the sump frame forward away from the main frame. The main frame carries an electric motor driving a hydraulic pump for supply of fluid under pressure to fluid activated devices such as cylinders and hydraulic motors which are mounted on the main frame and on the sump frame. To connect the hydraulic pump on the main frame to fluid activated devices on the movable sump frame. sliding fluid joints are provided which eliminate the need for long flexible hose. The joints permit the frames to move relative to each other while maintaining a constant flow of fluid between the devices on the main frame and those on the sump frame. The sliding fluid joint comprises a cylinder and a longer hollow rod which passes longitu dinally through the cylinder. Fluid flows into the rod and passes through holes in the rod into the cavity formed between the rod and the cylinder. From there the fluid flows out of an opening in the cylinder sidewall to the fluid activated devices on the second frame. This structure allows the rod and cylinder to move relative to each other without affecting the flow of fluids between the main frame and sump frame.

6 Claims, 7 Drawing Figures FATENTEBAPR 81975 9.876 252 saw 1 0F 3 PATENTEDAPR 81975 SHEET 2 OF 3 'II III II III PATENTEDAPR 8l975 saamsu ig MINING MACHINE WITH APPARATUS FOR CONVEYING PRESSURIZED FLUID BETWEEN MOVABLE FRAMES BACKGROUND OF THE INVENTION This invention relates to mining machines and particularly to mining machines having two or more major components that move relative to each other. Hydraulic devices are used extensively on large heavy duty movable equipment such as mining machines or mine conveyors. The hydraulic devices may include either cylinders or hydraulic motors which act to lift. move or propel certain parts of the machine. Usually the machine has one electric motor that drives the hydraulic pump. The pump. in turn. supplies fluid under pressure to the fluid activated devices such as the cylinders or hydraulic motors. The fluid activated devices are conventionally connected to the pump by hydraulic hoses. Usually the pump and fluid activated devices are stationary relative to each other. and the connecting hoses are likewise stationary. However. it is sometimes necessary for the frame on which the fluid activated devices are located to move relative to the frame on which the pump is mounted. In such instances the prior art has conventionally used the usual hydraulic hose. The hoses are simply made longer and are allowed to flex as the frames move relative to each other.

For small diameter hoses in clean environments. this flexing is not particularly harmful to the hose. How ever. for inch diameter hose or larger the periodic flexing is detrimental to the hose. Continued flexing of the large hose leads to its eventual early failure. Then there is the usual equipment and operation downtime attendant with such a failure.

Furthermore. in harsh environments such as mines. there is the additional problem that the free hanging hose is exposed to falling ore or other debris. Typically. to avoid this problem a large enclosure is built around the hose.

For most heavy weight mining machines. the rotary cutting drum is advanced or sumped into the mine face by simply propelling the total machine forward on its crawlers. However. the coefficient of friction for moving crawlers is substantially less than that for nonmoving crawlers. Therefore. for lighter weight. low seam mining machines it would be advantageous to be able to lock the crawlers and advance the rotary drum by means of a connecting but movable sump frame. Since hydraulic devices are mounted on both the crawler frame and on the movable sump frame which carries the rotary drum. some provision must be made for transfer of hydraulic fluid between the movable frames. Conventionally. the fluid transfer means has been a long flexible hose encased in a large protective enclosure. Such protective enclosures take up a considerable amount of space.

SUMMARY OF THE INVENTION In view of these considerations. it is an object of the present invention to provide improved apparatus for transfer of pressurized fluid between two frames that move relative to each other.

A further object of the invention is to provide a hydraulic fluid transfer device which has a constant volume of fluid and metal components in the system so that there is no change in the compression of the fluid flowing through the device.

Another object of the invention is to provide a sliding fluid joint for transfer of hydraulic fluid that is more reliable and maintenance free than the conventional hy' draulic hose because it eliminates the need for flexing of the hose.

Still another object of the invention is to provide a mining machine with an improved fluid transfer means for supplying pressurized hydraulic fluid from a hydraulic pump on a main frame to fluid activated devices on a front sump frame that moves relative to the main frame.

The present invention accomplishes the above objectives by providing a cylinder in combination with a hollow rod which passes longitudinally through the cylinder in fluid transfer relationship. The hollow rod is smaller in diameter than the cylinder and about twice the length. A seal is disposed near each end of the cylinder to form a closed cavity between the outer surface of the rod and the inner surface of the cylinders. The seals also allow the rod to slide easily back and forth through the cylinder. One end of the rod is closed and the other end is connected to a source of hydraulic fluid. The rod also has an opening at its center region to allow flow of fluid from the rod into the cavity between the rods outer surface and the cylinders inner surface. The cylinder also has an opening in its sidewall for connection to the fluid activated device disposed on a separate frame.

In operation. the invention provides the following reversible fluid connection between a pump attached to one frame and fluid activated devices mounted on a second frame. The fluid from the pump flows into the rod and out of the holes in the center region of the rod into the cavity between the rod and the cylinder. From there it flows out the opening in the sidewall ofthe cylinder to the fluid activated devices on the second frame.

Since the cylinder and rod are able to move relative to each other. the system is able to accommodate similar relative motion between the two frames. As the rod moves relative to the cylinder. the volume of fluid in the system does not change. The volume of fluid in the hollow rod remains constant. And the volume of fluid in the cavity between the rod and the cylinder remains constant. Also. the volume of metal in the rod and cylinder system remains constant and is not changed by the relative motion of the rod and cylinder.

The present invention was initially developed for and is of particular utility to small. low seam mining machines. As such. it is described herein in its relationship to such mining machines. However. it has application to other fields where similar problems of fluid transfer between moving parts exist.

DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of a mining machine having a movable front sump frame incorporating the sliding fluid joints of the present invention.

FIG. 2 is another perspective view of the mining machine shown in FIG. I, with the movable front frame. the sliding fluid joints in the extended position and the auger in the raised position.

FIG. 3 is an enlarged side elevational view partially in cross section ofa single sliding fluid joint of the present invention with the full extended position of the joint shown in broken lines.

FIG. 4 is a cross sectional view taken substantially along line 4-4 of FIG. 3.

FIG. 5 is atop plan view of a plurality of the sliding fluid joints mounted in tandem.

P16. 6 is a side elevational view of another embodiment of the invention wherein two of the sliding fluid joints are placed end to end.

H6. 7 is a side elevational view of the sliding fluid joints of FlG. 6 with both joints in the extended position.

DESCRlPTlON OF THE PREFERRED EMBODIMENT A continuous mining machine 10 shown in F163. 1 and 2 of the drawings has a mining head 14 with a r0 tary drum 40 for cutting and breaking material from a mine face. Endless crawler tractor treads 16, disposed one on each side of the main frame. propel the machine. A second frame or sump frame 12 is mounted on top of the main frame 11. The sump frame is connected to the main frame by means of a tongue 17 and groove [not shown) arrangement which enables the sump frame to be moved horizontally away from the main frame. The sump frame 12 is moved forward and backward by a pair of hydraulic cylinders 18 located on opposite sides of the machine one of which is visible in FIG. 2. Each hydraulic cylinder 18 is connected at one end to the main frame 11 and at the other end to the sump frame 12. By activating the hydraulic cylinders. the rotary drum 40 is advanced or sumped into a mine face.

Because the chassis of the mining machine is config ured with a central sliding sump frame. it permits the crawlers 16 to remain locked while advancing or sumping the rotary drum or augers 40 into a mine face. This design takes advantage of the fact that the static coefficient of friction between the fixed crawlers and the floor is approximately 50 percent greater than the dynamic coefficient of friction between moving crawlers and the floor. The hydraulic cylinders 18 act to move the sliding sump frame 12 forward. The sliding sump frame 12 carries the rotary drum head 40, gathering head 20 and conveyor assemblies 21 and 22 in its forward and rearward movement.

The mining head 14 has a boom that extends forwardly to support the rotary drum 40 at the front end of the sump frame 12 of the mining machine 10. The boom 31] is connected by a pivot structure 31 to the sump frame.

The mining head 14 is pivotally mounted on the pivot structure 31 and is moved upwardly and downwardly by a pair of hydraulic cylinders (not shown) located on opposite sides of the sump frame 12. Each of these hydraulic cylinders is pivotally connected at one end to the sump frame 12 and at the other end to the boom 30.

The rotary drum 40 is driven by a pair ofelectric mo tors 34, one of which is shown in FIG. 2, that are disposed at opposite sides of the sump frame 12. The mo tors 34 drive motor gear transmissions and a clutch and brake mechanism (not shown). Each of the clutches is connected by means of a drive sprocket (not shown) to a drive chain 38 that delivers drive by means of a second sprocket wheel 37 to the rotary drum 40.

The forward sprocket wheel 37 is fixed to a shaft 41 which extends transversely to the frame 12. Fixed to the shaft are three auger cutting sections 42, 43 and 44. Each auger section comprises a pair of helical blades 45 having their inner peripheries fixed securely to the adjacent portion of the casing 48 of the shaft 41 and the outer peripheries of a substantial constant radial extent. The pitch of the blades 45 of each section 42, 43, 44 is such that when rotated they will serve to convey material inwardly toward the forward end of the cen trally disposed gathering conveyor 21.

The outer periphery of each helical blade 45 of each auger section 42, 43, 44 has secured thereto a plurality of spaced bit holders 46 arranged to receive bits 47 of conventional structure that extend outwardly from the periphery of the blades 45. The bits on each blade are spaced apart equally in a longitudinal or axial direction.

There is a gathering head 20 at the front of the mining machine 10 below the boom 30. The gathering head 20 has an apron or deck 23, with its leading edge at the floor. A vertical hinged dozer blade 24 extends along the back edge of the apron 23 to provide a surface against which the helical auger may move the coal. A small mat conveyor 21 extends toward the front of the apron 23. This small conveyor 21 operates in conjunction with the spiral augers 42, 43, 44 and the vertical dozer blade 24 to move the mined material back to a discharge conveyor 22. The discharge conveyor 22 moves the mined material from the forward end of the mining machine to its rear end, at which it is discharged to other conveying apparatus (not shown) for removing the mined material from the mining place.

A third electric motor (not shown) is located in an enclosure 50 on the main frame 11. Driving connections from this motor drive hydraulic pumps, (not shown) also located in the enclosure 50, which provide hydraulic fluid with a pressure of about 2,000 psi. This fluid is used to operate the hydraulic cylinders for the mining heads 14, the hydraulic cylinders for the gathering head 20, the hydraulic cylinders (not shown) for the discharge conveyor boom and the hydraulic motors (not shown) which run the mat conveyor 21 and the conveyor 22 and the hydraulic cylinders 18 which move the sump fram.

Some of the fluid activated devices such as cylinder 18 which are powered by the pressurized fluid from the pump are located on the main frame 11. These devices are connected to the hydraulic pump by conventional hydraulic pipes or hose lines (not shown). However. some of the fluid activated devices such as the hydraulic cylinders for the mining head 14 and the hydraulic motors for the conveyors 21 and 22 are located on the movable sump frame 12. To accommodate the movement of the sump frame 12 relative to the main frame 11, special fluid transfer devices or sliding fluid joints are provided for maintaining a constant flow of hydraulic fluid from the pump 51 to the fluid activated devices on the sump frame 12. An enclosure 71, 72 is provided on either side of the main frame to house the sliding joints 60.

FIG. 3 illustrates a single sliding fluid joint 60 for transfer of fluid between the hydraulic pump on the main frame 11 and the fluid activated devices on the sump frame 12. The sliding fluid joint 60 comprises a cylinder 61 having a hollow rod 65 passing longitudinally therethrough. The inner wall surface 62 of the cylinder 61 is spaced away from the outer surface 69 of the rod 65 to allow free flow of fluid in the space 70 therebetween. To close off the open ends between the cylinder 61 and the rod 65, conventional sleeve bushings 53 are disposed in grooves 58, 59 at either end of the cylinder. The sleeve bushings S3, 153 include static seals 54, 154 which rest against the inner surface 62 of the cylinder. and dynamic seals 55, 155 which allow movement of the rod 65 through the interior of the cylinder 61. All of the seals are made of conventional type sealing material. Also near the outer end of each seal there is a conventional rod wiper 56, 156. Finally. rctaining rings 57, 157 are inserted in the grooves 58. 158 at either end of the cylinder to hold the sleeve bushing 53, 153 in place.

The hollow rod 65 extends through the cylinder 61 and is free to travel back and forth relative to the outer cylinder 61. The hollow rod is closed at one end 66 and is threaded at the other end 67 for connection to the supply of hydraulic fluid (not shown). Cross holes 68 are made in the center region of the rod 65 to allow free flow of fluid between the interior of the rod and the space between the cylinder and rod.

The cylinder 61 has a threaded opening 64 in its wall to which a right angle fixture 63 is affixed for connection to a hose. pipe or similar fluid conveying means 74. thus completing the fluid connection between the pump on the main frame 11 and fluid activated devices on the sump frame 12.

In operation. fluid under pressure is supplied from the hydraulic pump (not shown) to the interior of the rod 65. The fluid fills the rod and flows through the cross holes 68 in the center region of the rod filling the space 70 between the outer surface 69 of the rod and the inner surface 62 of the cylinder. The fluid then exits through the opening 64 in the sidewall of the cylinder to be conveyed to the hydraulic devices. It can be seen that by means of this invention a continuous uninterruptcd path is available for the pressurized fluid to travel from the pump to the fluid activated devices.

The opening 67 into the rod. the cross openings 68 in the center region of the rod and the exit opening 64 in the cylinder wall are approximately all equal in cross sectional area. In addition. the cross sectional area of the space 70 shown in FIG. 4 between the outer surface 69 of the rod and the inner surface 62 of the cylinder also approximates the cross sectional area of the other openings 67, 68. and 64. All of these openings are about equal in total cross sectional area so that the resistance to fluid flow through the system is constant.

This rod and cylinder sliding fluid joint 60 performs no work. Theoretically there is no horsepower loss caused by the relative movement of the rod 65 and the cylinder 61. The only force which must be overcome to move the rod relative to the cylinder is the frictional force between the outer surface 69 of the rod and the surface of the seals 55, I55 and wiper blades 56.

It is noteworthy that there is no change in fluid volume or in the volume of metal in the system. Whether the cylinder. 61 is in the retracted position as shown in FIGv 3 or whether it is in its extended position as shown by the broken lines 90 in FIG. 3, the volume of fluid in the system remains constant. as does the volume of metal. Thus there is no compression of fluid as the cylinder 61 moves relative to the rod 65.

The flow of fluid through the sliding joint may be in either direction. The fluid flow may be from the rod 65 into the cylinder 61 or the flow may be from the cylinder 61 into the rod 65. Thus. the slip joint 60 may be used for hydraulic motors. wherein the flow may be in either direction depending on the operation of the motor.

FIG. 5 shows the arrangement of a bank of sliding joints 60 installed for a mining machine operation. Because of the harsh nature of the mining environment. the sliding joint assemblies are enclosed in a metal box 71. Except for their position in the box 7], the individual joint assemblies 60 are identical and the parts of each are identified by the same reference numerals. with the addition of a prime or a double prime. The hollow rods are attached securely at either end to the box 71 which is then bolted to the main frame 11. Right angle pipe elbows 63 are attached to each of the threaded cylinder openings 64. Pipes 80 are then connected to each of the outlets of the elbows 63. It is important that since the pipes 80 are rigid and move with the cylinder 61 relative to the rod 65, that the pipes 80 be exactly parallel to their corresponding rods 65. This parallel configuration minimizes binding of the rods 65 against the seals 55 in the cylinder 61.

Since the cylinders always move together in parallel fashion. they are hooked together by a bar 59 which gives added stability to the system. In a similar manner another stabilizing bar 159 holds the exiting pipes 80 together.

The ends of the box enclosure 71 are closed off except for the openings 73 which accommodate the movement of the connecting pipes 80 therethrough. The openings 73 are lined with sealing material (not shown) to make the box 71 substantially airtight. A slight differential in pressure is created when the sump frame 12 is extended moving the pipe 80 out of the box 71. Therefore. dust or other foreign material would be drawn into the box were it not airtight.

The present invention may be used in most machines where flexing of hydraulic hose would be encountered. The only restriction is that room must be provided for the long rod 65 whose length must necessarily be twice the amount of the desired extension. This length limitation results because the seals 55 of the cylinder 61 cannot be allowed to cover the cross holes 68 in the center of the rod. The cross holes in the rod must always open into the space formed between the rod and cylinder to assure a continuous uninterrupted flow between the two frames. As long as the rod and cylinder are adequately supported. the assembly may be made to any practical length allowed by the particular machine.

In the case of the mining machine 10 described herein, the sump frame moves about eighteen inches away from the main frame thus sliding joints are made to accommodate slightly more than eighteen inches of movement to assure the cross holes are never covered. Accordingly. the overall length of the retracted sliding joint assembly is approximately (40 inches and the extended length is about 68 inches 40 inches plus the 18 inch extension).

Rather than make one long sliding joint assembly. it may be more feasible or desirable to combine two joint assemblies end to end. FIGS. 6 & 7 show schematically how this might be done. A sliding joint assembly 260. 360 is secured to each frame 111. 112 so that the rods 165. 265 and cylinders 161, 261 are placed end to end and connected by a pipe 180. The cylinders and rods move relative to each other as previously described. and at their full extension have the configuration shown in FIG. 7.

In the mining machine application, the main frame I1 and sump frame 12 are rigidly held so that the only relative movement is a straight horizontal movement.

Thus. the end of the rod 65 and cylinder 61 maybe rigidly held without danger of binding or otherwise damaging the sliding joint assembly 60. However, for other applications it may be desirable to allow for some movement or play of the pieces of the assembly. This may be done by connecting the rod and cylinders to flexible hoses rather than to rigid pipes. In conjunction with the substitution of the flexible hoses. it may be advantageous to pivot the sliding joint assembly to enable the second frame to turn relative to the main frame as well as move away from or towards it.

Having thus described the invention. those skilled in the art will recognize various uses for and changes in the details and arrangement of parts without departing from the scope of the invention as it is defined by the appended claims. It is therefore respectfully requested that this invention be interpreted as broadly as possible according to the provisions of the patent statutes and limited only by the scope of the appended claims.

I claim:

I. A mining machine. comprising:

a main frame having a hydraulic pump mounted thereon for supply of hydraulic fluid under pressure. sump frame slidably mounted on the main frame to allow movement of the sump frame relative to the main frame. the sump frame having fluid activated devices mounted thereon;

a sliding fluid joint for transfer of hydraulic fluid from the pump on the main frame to the fluid activated devices on the sump frame. comprising:

a hollow longitudinal rod having an opening near one end for connection to fluid conveying means on one of the frames. the rod also having an opening in its sidewall near the center of the rod;

a hollow cylinder having an opening in each end for passage of the rod therethrough. the inner surface of the cylinder walls being spaced a sufficient distance from the outer surface of the rod sidewalls to allow flow of fluid in the space formed therebetween. the cylinder also having another opening in its sidewall for connection to fluid conveying means on the other frame; and

means allowing movement of the rod relative to the cylinder while maintaining the opening in the rod sidewall in communication with the space between the cylinder and rod. such that the hydraulic fluid can flow at a constant rate and pressure through the sliding joint notwithstanding movement of the sump frame relative to the main frame.

2. A mining machine as recited in claim l, wherein the rod is at least twice the length of the cylinder.

3. A mining machine as recited in claim 1. wherein the cross sectional area of the end opening in the rod, the area of the side opening in the rod, the area of the cylinder opening. and the cross sectional area of the space between the rod and the cylinder are approximately equal.

4. A mining machine as recited in claim I, wherein the connections of the rod and the cylinder to their respective frames are flexible mounts.

5. in a mining machine comprising a main frame having hydraulic fluid supply means mounted thereon. a sump frame supporting a mining head and mounted on the main frame in a manner allowing movement of the sump frame relative to the main frame for sumping the mining head into a mine face. and fluid actuated means mounted on the sump frame. wherein the improvement comprises:

means for conveying hydraulic fluid from the supply means to the fluid actuated means without any change in pressure or flow rate regardless of position or movement of the sump frame relative to the main frame, including:

a first rigid tube mounted on one of the frames and having an opening at one end connected to the fluid means on said one frame;

a second larger tube mounted on the other frame in sliding concentric spaced relationship about the first tube. the second tube being shorter than the first tube and having an opening in its sidewall connected to the fluid means on said other frame.

sliding fluid seals between the tubes at each end of the second tube forming the ends of an annular fluid transfer zone between the tubes. the first tube further having an opening in its sidewall in communication with the fluid transfer zone. said tubes being adapted to slide relative to each other when the sump frame moves relative to the main frame such that the opening in the sidewall of the first tube always remains in communication with the fluid transfer zone. and fluid under pressure can flow steadily through one tube. the fluid transfer zone. and the other tube at all times.

6. In a mining machine as recited in claim 5, the further improvement wherein the area of each of the openings in said tubes and the area of the cross section of the annular fluid transfer zone between said tubes are approximately equal such that there is no change in the pressure or flow rate of fluid flowing through the fluid conveying means. 

1. A mining machine, comprising: a main frame having a hydraulic pump mounted thereon for supply of hydraulic fluid under pressure; a sump frame slidably mounted on the main frame to allow movement of the sump frame relative to the main frame, the sump frame having fluid activated devices mounted thereon; a sliding fluid joint for transfer of hydraulic fluid from the pump on the main frame to the fluid activated devices on the sump frame, comprising: a hollow longitudinal rod having an opening near one end for connection to fluid conveying means on one of the frames, the rod also having an opening in its sidewall near the center of the rod; a hollow cylinder having an opening in each end for passage of the rod therethrough, the inner surface of the cylinder walls being spaced a sufficient distance from the outer surface of the rod sidewalls to allow flow of fluid in the space formed therebetween, the cylinder also having another opening in its sidewall for connection to fluid conveying means on the other frame; and means allowing movement of the rod relative to the cylinder while maintaining the opening in the rod sidewall in communication with the space between the cylinder and rod, such that the hydraulic fluid can flow at a constant rate and pressure through the sliding joint notwithstanding movement of the sump frame relative to the main frame.
 2. A mining machine as recited in claim 1, wherein the rod is at least twice the length of the cylinder.
 3. A mining machine as recited in claim 1, wherein the cross sectional area of the end opening in the rod, the area of the side opening in the rod, the area of the cylinder opening, and the cross sectional area of the space between the rod and the cylinder are approximately equal.
 4. A mining machine as recited in claim 1, wherein the connections of the rod and the cylinder to their respective frames are flexible mounts.
 5. In a mining machine comprising a main frame having hydraulic fluid supply means mounted thereon, a sump frame supporting a mining head and mounted on the main frame in a manner allowing movement of the sump frame relative to the main frame for sumping the mining head into a mine face, and fluid actuated means mounted on the sump frame, wherein the improvement comprises: means for conveying hydraulic fluid from the supply means to the fluid actuated means without any change in pressure or flow rate regardless of position or movement of the sump frame relative to the main frame, including: a first rigid tube mounted on one of the frames and having an opening at one end connected to the fluid means on said one frame; a second larger tube mounted on the other frame in sliding concentric spaced relationship about the first tube, the second tube being shorter than the first tube and having an opening in its sidewall connected to the fluid means on said other frame; sliding fluid seals between the tubes at each end of the second tube forming the ends of an annular fluid transfer zone between the tubes, the first tube further having an opening in its sidewall in communication with the fluid transfer zone, said tubes being adapted to slide relative to each other when the sump frame moves relative to the main frame such that the opening in the sidewall of the first tube always remains in communication with the fluid transfer zone, and fluid under pressure can flow steadily through one tube, the fluid transfer zone, and the other tube at all times.
 6. In a mining machine as recited in claim 5, the further improvement wherein the area of each of the openings in said tubes and the area of the cross section of the annular fluid transfer zone between said tubes are approximately equal such that there is no change in the pressure or flow rate of fluid flowing through the fluid conveying means. 